302 SURFACE GEOLOGY. 
these hills, is very irregular, consisting of hills, ridges, and rounds, with bowl-shaped 
hollows which frequently contain ponds. This feature has led some to regard these 
deposits as similar to kames.* Their material, however, is very different from that of 
the kames, which consist principally of stratifiéd water-worn gravel, rarely containing 
any large or angular boulders, but frequently intermixed with layers of sand. 
The conclusion of Mr. Clarence King, that this island, which he examined, forms 
part of a terminal moraine of the continental ice-sheet, seems to explain the accumula- 
tion of the till in this remarkable series of hills. The border of the ice-sheet probably 
remained almost stationary through a long period, in which the materials that it con- 
tained were being continually brought forward and deposited at this line of its melting. 
In many places these would be pushed into very irregular heaps and ridges by retreats 
and advances of the ice-margin. At the same time we should also expect that thick 
beds of ground-moraine would be gathered beneath the ice near its termination. The 
withdrawal of the glacial sheet would then leave these deposits as upper and lower till, 
one overlying the other, in a long but broken and undulating series of hills. 
This terminal moraine does not, however, mark the farthest limit reached by the 
glacial sheet, which at one time extended six or seven miles beyond the Elizabeth 
islands, as shown by the prominent range of drift hills, which forms the north-west 
part of Martha’s Vineyard. The origin of Cape Cod also seems to have depended upon 
this greater extension of the ice-sheet. Its terminal front appears to have continued 
from Martha’s Vineyard north-easterly across Barnstable, thence to the east and north 
along the inner shore of the cape to Truro, which it probably crossed, extending on- 
ward to the north-east. This seems to be the outmost line at which we can assert the 
former presence of the continental ice-sheet. 
Cape Cod, east from Sandwich, consists almost entirely of modified drift. Through 
Barnstable this is disposed in kame-like ridges, knolls, and small plains, separated by 
crooked and bowl-shaped depressions. The material here is gravel and sand, often 
obliquely bedded, with frequent boulders which appear to have been dropped upon 
these stratified deposits from floating ice. From Barnstable to South Wellfleet the 
surface is mainly level, consisting of plains of fine gravel or sand, and boulders are 
rarely seen. These plains vary in height from 25 to 75 feet above the sea. From 
South Wellfleet to High Head in the north part of Truro, the contour on the west side 
of the cape is again in very irregular kames, which are composed of gravel and sand 
with only rare boulders. These deposits, like those in Barnstable, rise to a height 100 
to 150 feet above the sea. The east side of the cape is here a nearly continuous bluff 
of this height, horizontally stratified, being evidently a remnant of a nearly level plain, 
the east part of which has been washed away by the sea. Thick beds of clay have 
been exposed ata few points. At the Clay Pounds, near Highland light, the section 
is sand at the top, about 4o feet; finely laminated blue clay, also about 4o feet; then 
* Proceedings of the Boston Society of Natural History, vol. xix, pp. 59-63; and American Naturalist, 
vol. xi, pp. 674-680. 
